Thermal switch



Sept'. j28,

r il l@ l l I R. H. SCHMITT THERMAL SWITCH Filed June 29, 1934 Inventor:

Ric/Hamel H. Schmitt www ' Hi Attorney.

rammed sept. 21s, 1957 UNITED STATES PATENT OFFICE to General ElectricNew York Application June 29,

9 Claims.

lMy invention relates to thermal switches, more particularly to switchesarranged to control vthe starting of motors, and has for an object theprovision of a simple, inexpensive and reliable switch of thischaracter.

In carrying out my invention in one form there.

. erating handle is operated'from the .on to the olf position.

For a more complete understanding of my invention, reference should nowbe had to the accompanying drawing wherein I have shown in Fig. 1 a planview `of switch'embodying my invention; Fig. 2 is a sectional elevationtaken on the line 2--2 of Fig. l; Fig. 3 is a perspective view of` theswitch, while Fig. 4 is a plan view showing the relation of the thermaloverload devices with a portion of the tripping mechanism located on thelower or left-hand side of the insulating base.

Referring to the drawing, I have shown my invention in one form asapplied to a three-pole switch III provided with a base II formed ofinsulating material. The base is 4secured within a metal switch box I2by means of brackets I3 and I4 which cooperate lwith ledges I5 and I6formed integrally with the base member II, and by screws I8 and I9,which screws extend through vthe insulating base member and intoscrewthreaded engagement with the switch box I2.

A switch member 22, formed of insulating material and pivotally mountedon a pivot pin 23 extending vthrough the respective sides vof a U-shapedmetallic frame 24, supports the movable bridging contacts v25, 26 and21. The frame 24 is mountedbn the right hand side or upper side ot thebase II as viewed in Fig. 2. The member 22 and the movable contacts arenormally biased to an open circuit position by means of a spring 28wound about the pivot pin 23, one end of the spring bearing against thecross member of the frame and its other end bearing against a pin 30 5ucarried by the switch member. The switch mem` ber 22 is operativelyconnected to an operating handle 3i by means of a toggle link 32connected by the pin 30 tothe switch member and a toggle link 33connected at one end by a pivot pin 34 Vmi to the handle 3i, the twolinks being connected Company, a corporation of 13934, serial No.733,005

(ci. l20o-116) together by a knee pivot pin 31. The collapsible drivingconnection or toggle formed by the links 32 and 33 is normallymaintained in a straightened and slightly overset position, as shown inthe drawing, by a coil spring 38 wound about the knee pivot pin 31. Across portion 33a of the link 33 forms a stop for the toggle in theoverset position, i. e. the position when the knee pivot pin 31 islocated slightly below a line taken through the centers of the pins 30and 34 of Fig. 2. Consequently, the force of the spring 28 does not tendto collapse the toggle.

When the handle 3i is in the fully closed position, shown in Fig. 2, thebias of the spring 28 is applied directly by the toggle to the handle ina direction to hold the handle in its on or fully closed position. Thusthe bias of the spring 28 is applied to the handle in the direction oi aline extending from the center of the pin 30 through the center of pin34. This line of the applied force passes below the pivot pin 3Ia of thehandle and thereby tends to rotate the handle in a counter-clockwisedirection as viewed in Fig. 2. The on position of the switch, however,is determined by the engagement of the projection 39 on the handle witha pin 4U extending between opposite sides of the frame 24. Thecompression springs 4I', 42 and 43 associated with the respectivemovable bridging contacts 25, 26 and 21 and resiliently securing thecontacts on the switch member 22 are 4compressed as the movable con-vtacts are operated into engagement with their associated pairs ofstationary contacts only one pair of which, the contacts 46 and 41,being shown. Besides insuring a strong contact pressure and permittingautomatic adjustment for irregularities in the contact surfaces, thecompression springs 4I-43, inclusive, assist in accelerating the switchmember 22 during its operation to its open circuit position. Byrotatingl the switch handle 3i in a clockwise direction, as viewed inFig. 2, the pivot pin 34 is rotated to the opposite side ofthe pivot pin3Ia so that the springs 28, 4I ,'42 and 43, quickly open the switch.

The three-pole switch I0 is particularly applicable to the control of athree-phase motor and in order to insure the automatic operation of theswitch to its open circuit position in the event of an overload on anyone of the phases, two thermal overload devices 50 and 5I are connectedin spaced relation with a'stationary bushing 54, both the coil andbushing being mounted on the right hand or upper side of the base. Ashaft 55, normally rigidly secured to the bushing 54 by means of asolder lm, extends through the base and rigidly supports at one end areleasing gear 56, shown in Fig. 4. The'thermal overload device 5|provided with a releasing gear 51 is of identical construction with thedevice 50.

The .tripping or release mechanism operated in respnse' to there'leaseof either one, or both, of the gears 56 and 51 consists of a bifurcatedtripping lever 60 pivoted on the pin 40. One arm 6| fof this lever,located on the upper side, as viewed in the drawing, of a resettingextension 62 formed integrally with the switch member 22, is arrangedfor movement into engagement with the knee portion of the toggle. Theother arm 63 located on the opposite or lower side of the resettingextension 62 extends throughan aperture Ila provided in the base andthrough a slot 64 provided in a floating latch 'member 65 to which aresecured t'wo latching pawls 66 and 61. The pawl 66 is pivoted at 10 toone end of the latch member, the opposite end 1| of the pawl engagingthe gear 56. Similarly, the pawl 61 is pivoted at 12 to the latch member65 while its opposite end 13 engages the gear 51. A tension spring 15connected between a stationary supporting plate 16 and the end 63a ofthe arm 63 of the tripping lever serves to bias the tripping member 60for movement of its other arm 6|` to break the toggle.

leasing gears 56 and 51 by a leaf spring 80 carried by the plate 16.This plate 16, secured to the bottom of the base by a screw 8|; (Fig. 2)has tripping mechanism on opposite sides of the base Furthermore; sincethe overload tripping mechanism is concealed in its position below thebase, there is less likelihood that the operation of the switch will beimpaired due to tampering by the unskilled.

Continuing with the description of my inven` tion, it will be assumedthat a predetermined overload current flows through the heating coil 53f tocause the release of the gear 56 forrotation.A

The tension spring 15 thereupon rotates the latch member `65 and thearm'66 in a counter-clockwise direction about the pivot pin 12, asviewed in Fig.l

4, the arm 61 being held stationary by its associated gear 51. The arm63 of the tripping lever 60 extending through the slotted latch member65 and rotating with it, moves the other arm 6| against the knee of thetoggle and thereby moves the knee pivotpin 31 upward, as viewed in thedrawing, to bre kfoncollapse the toggle. A very small movemei isrequired since the toggle is'but slightly overse the opening of theswitch occurring very quickly due to the combined action of thesprings28 and 4|-43, inclusive.

As the opening movement of the switch member 22 begins, its resettingextension 62 engages the arm 63 to return the tripping member 60 to itsoriginal position, against the force applied by the spring 15,'theswitch opening springs being many times stronger than the spring 15. Thereturn movement of the arm 63 rotates the latch member 65 and the pawl66 about the pivot pin 12 to their original positions completing .theautomatic resetting of the tripping mechanism.

The pawls' 66 and 61 are biased towards the respective re-l It will beobserved that coil spring 38 encircling the knee pivot pin 31 biases thetoggle links 32 and 33 to their straightened positions. This spring 38functions to straighten the toggle, after the' switch has tripped open,and in so doing rotates the handle 3| rfrom its on position to its oiposition. Consequently to reclose the switch it is only necessary tomove the handle 3| to its thereby prevent the closing of the switch.

Since the toggle or collapsible driving connection is located betweenthe handle 3| and the switch member 22the switchis trip free; that is,the overload` opening of the switch occurs irrespective of the positionof the handle 3|. Similarly, the automatic resetting of the thermaltripping mechanism isindependent ofthe position of the handle 3|. f

In case of an overload which frees the gear 51, it will be understoodthat the latching member 65 and the paWl 61 rotate about the pivot pin16 to operate the tripping member 60 to trip the switch. In case of anoverload which frees both gears 56 and 51, the latching member 65, pawls66 and 61 and the tripping member 60 move longitudinally to trip theyswitch to the open circuit position. In each case therigid engagement ofthe resetting extension 62 withthe arm 63 vof the tripping'member 60resets the thermal tripping mechanism.

While I have shown a particular embodiment of my invention, it will beunderstood, ofl course,

that I do not Wish to be limited thereto since many modifications may bemade, and I, therefore, contemplate by the appended claims to cover anysuch modifications as fall within the true spirit and scope of myinvention. f

What I claim asnew and desire to secure by Letters Patent of the UnitedStates, is:-`

l. A switch comprising a base formed of insulating material providedwith an aperture, a switch member, means mounting said switch member formovement between open and closed circuit positions, an opening springfor biasing said switch member to said open circuit position,

an operatinghandle, pivot means mounting said handle for rotationbetween on and oi positions, a collapsible toggle pivotally connectingsaid handle and saidswitch member and normally forming an operatingconnection therebetween, said handle when rotated from its off to its onposition operating said switch member to said closed circuit positionagainst the bias of said opening spring, a trip member biased for'movement from one position to a second position to collapse saidtoggle, said trip member extending through said aperture, a thermalresponsive device on the opposite side of said base from said switchmember restraining said trip member against movement from said oneposition but Operable on overload to free said trip member to operatesaid switch member to said open circuit position, and means operablewithv said switch member as said switch member moves to its open circuitposition to return said trip member to said one position.

2. A switch comprising a switch member, pivot; means pivotally mountingsaid switch member for movement between open and closed circuitpositions, said switch member being provided with an extension adjacentsaid pivot means, a spring normally biasing said switch member to saidopen circuit position, an operating handle for said switch, toggle meansbetween said handle and said yswitch member normally forming anoperating connection between them and operable to hold said switchmember in said closed circuit position against the bias of said spring,a trip member for breaking said toggle means to permit the openingmovement of said switch member by said spring, said extension engagingsaid trip member to return said trip member to its normal position assaid switch member moves to its open circuit position.

3. A multipole switch comprising a plurality of stationary contacts, aplurality of movable contacts, a switch member Vformed of insulatingmaterial, means mounting said movable contacts on said switch member,pivot means pivotally mounting said switch member for movement between.open and closed circuit positions, said switch member being providedwith'an upturned extension adjacent said pivot means, a spring normallybiasing said switch member to said open circuit position, toggle meansfor holding said switch member in said closed position, a trip memberfor said toggle means, pivot means mounting said trip member'adjacentsaid extension, a spring biasing said trip member from a normal positionto release said toggle means, a thermal device for restraining said tripmember in a normal position against movement by its associated spring,said thermal device being responsive to overload current andoperablethereby to free said trip member to open said switch. said extensionduring the opening of said switch engaging said trip member to returnthe same to its normal position.

4. In combination, a multi-pole switch com` prising a switch memberformed of insulating material, pivot means pivotally mounting saidswitch member for movement between open and closed circuit positions, anoperating handle movable between on and oi positions, a normally rigid loperating connection between said handle and said switch member, a tripmember provided with an extension normally maintained in a normalposition and out oi engagement with said operating connection, a springbiasing said trip memstraining memberprovided with two arms, gear wheelsnormally maintaining said arms in ilxed position, solder films for ,saidwheels normally,

maintaining them stationary and responsive, to overload current to freesaid gears for rotation, the resulting movement of said restrainingmemberinto engagement with said trip member efi'ecting the opening ofsaid switch, and means forming a connection between said switch memberand said trip membereil'ective during thel opening of said switch toreset said thermal device.

5. A thermal switch comprising aiswitch member operable between open andclosed circuit positions, pivot means for said switch member, anextension provided on said switch member adjacent said pivot means, abiiurc'ated trip member having its respective arms located on oppo- .f

site sides of said extension,1 means biasing said switch member to saidopen `circuit position, toggle means for holding said switch member insaidclosed circuit position, one arm of said trip member being operableinto engagement with said toggle means to cause the operation of saidswitch member to its open circuit position, a pair of .solder lmoverload devices, a restraining member provided with a pair of armsrespectively engaging said solder film devices, said restraining memberbeing provided with a slot into which said other arm of said trip memberextends, biasing means for biasing said trip member to trip saidlatching means, said restraining member and said arms preventingmovement of said trip member except during the occurrence of an overloadon one or the other of ,said solder' l illm devices.

6. A thermal switch comprising a base formed of insulating material; aswitch member, means pivotally mounting said switch member on one sidevof said base for movement between openA and closed circuit positions,biasing means for biasing said switch member to said open circuitposition, a resetting extension provided on said switch member adjacentsaid pivot means, a bifurcated trip member having its respective armslocated on opposite sides of said extension, toggle means for holdingsaid switch member in said closed circuit position, means biasing saidtrip member for movement of one arm into engagev ment with` said togglemeans to cause the opera- "said trip member in a normal position, saidrsetting extension` rigidly. engaging said second arm of said tripmember to resetsaid trip member after rthe release 'of said' trip memberby said thermal overload means upon movement of the switch member tosaid open circuit position.

'7. A switch comprising a base formed of insulating material, a contactsupporting switch member, means mounting said switch member on one sideof s'aidbase for movement between open and closedcircuit position, anopening spring normaljly biasing said switch member to said open circuitposition, a switch operating handle movable be- -tween on and oipositions, a double link. toggle connected between said handle and saidswitch member for holding said switch member'in said closed positionagainst the bias of said opening spring, a resetting extension securedto said switch member adjacentsaid pivot means, a bifurcated trip memberpivoted at one end adjacent said hant ment froma normal position tobreak said toggle, a pair of solder-film overload devices located onoppositesides of said second arm of said trip member, and latching meansmounted on said opposite side of said base and normally engaging saidsecond arm of said trip member and said overload devicesfor holding saidtrip member in said normal positio'n, said resetting extension rigidlyenmember for biasing said trip member for movegaglng said second'arm assaid switch member moves to its open circuit position to return said,

trip member and said latching means to their nor- ,mal positions againstthe bias oi said 'tripping 8. Aiswitch comprising a switch arm, means'pivotally mounting said switch arm at one end, a resetting extension onsaid switch arm adjacent said pivot extending substantially at rightangles with respectl tosaid switch arm, switch contacts carried on theother end of said arm, means biasing said switch arm from a closed to anopen circuit position, an operating handle, a releasable operatingconnection between said handle and said switch arm for maintaining saidswitch arm in said closed position, a trip member biased for movement torelease said connection, an overload responsive device normally holdingsaid trip member against its bias, said trip member having a portionarranged to be engaged by said resetting extension upon movement of saidswitch member to its open circuit position after release ingsubstantially at right angles 4with respect td toggle being normallyoverset to hold said switch arm in said closed position, a trip memberbiased for movement against said togglel to thereby release-saidoperating connection, thermal overload responsive means Afor holdings'aid trip member against its bias, said trip member having a portionarranged to be engaged by said resetting extension when said switch armmoves to said open circuit position whereby said trip member is returnedto its original position for engagement by said thermal overloadvmeans.

RICHARD H. SCHMI'I'I.

